Vacuum operated swimming pool cleaners are today well known and widely used, especially for cleaning domestic swimming pools. Most of these utilize an interruption of the water flow induced through the machine to impart a step-wise movement to the machine across the surface to be cleaned. While this movement takes place dirt on the surface is entrained in the water which flows through the machine to the pool filter.
U.S. Pat. No. 5,737,791 discloses an invention in which a reciprocating shuttle is made to cross a throat in an outlet passage from a pool cleaner in order to cause an interruption in the flow. The shuttle and the sleeve in which it operates are made to reduce friction. The front and back of the shuttle have the same area over which the reduced pressure in the pool cleaner is caused to act during use to move the shuttle. The dimensions of the passage conveying pressure to the back of the shuttle must also be calculated to cause this shuttle movement.